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Detailed diagram of lipid bilayer of cell membrane. The cell membrane, or plasma membrane, is a selectively permeable [citation needed] biological membrane that surrounds the cytoplasm of a cell. In animals, the plasma membrane is the outer boundary of the cell, while in plants and prokaryotes it is usually covered by a cell wall.
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
If a typical mammalian cell (diameter ~10 micrometers) were magnified to the size of a watermelon (~1 ft/30 cm), the lipid bilayer making up the plasma membrane would be about as thick as a piece of office paper. Despite being only a few nanometers thick, the bilayer is composed of several distinct chemical regions across its cross-section.
Cross-sectional view of the structures that can be formed by phospholipids in an aqueous solution. A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the cell and another.
The red blood cell membrane comprises a typical lipid bilayer, similar to what can be found in virtually all human cells. Simply put, this lipid bilayer is composed of cholesterol and phospholipids in equal proportions by weight.
3–4 μm – size of a typical yeast cell [86] 5 μm – length of a typical human spermatozoon's head [87] 6 μm – thickness of the tape in a 120-minute (C120) compact cassette [88] 7 μm – diameter of the nucleus of a typical eukaryotic cell [citation needed] about 7 μm – diameter of human red blood cells [89]
The cell nucleus (from Latin nucleus or nuculeus 'kernel, seed'; pl.: nuclei) is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells , have no nuclei , and a few others including osteoclasts have many .
Schematic of size-based membrane exclusion. A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles.